1. Field of the Invention
The present invention relates to a flame retardant aromatic polycarbonate resin composition. More particularly, the present invention is concerned with an aromatic polycarbonate resin composition comprising: a resin component (A) mainly comprising an aromatic polycarbonate, a solid inorganic compound (B), at least one compound (C) selected from the group consisting of an organic acid, an organic acid ester; and an organic acid anhydride, at least one organic acid metal salt (D) selected from the group consisting of an organic acid alkali metal salt and an organic acid alkaline earth metal salt, and a fluoropolymer (E), wherein the compound (C) is present in an amount wherein a mixture of the inorganic compound (B) and the compound (C) exhibits a pH value of from 4 to 8. The aromatic polycarbonate resin composition of the present invention is advantageous not only in that it exhibits an excellent flame retardancy without using a bromine compound or a phosphorus compound as a flame retardant (especially when a very thin shaped article is produced using the aromatic polycarbonate resin composition of the present invention, the produced very thin shaped article exhibits an extremely high level of flame retardancy as compared to the case where a conventional aromatic polycarbonate resin composition is used), but also in that it exhibits excellent properties with respect to melt stability, thermal aging resistance, resistance to moist heat, stiffness and impact resistance. Therefore, the aromatic polycarbonate resin composition of the present invention can be advantageously used for producing various shaped articles, such as an injection-molded article, and an extrusion-molded article.
2. Prior Art
An aromatic polycarbonate is a resin which not only has excellent mechanical properties (e.g., impact resistance) but also has excellent heat resistance. Therefore, an aromatic polycarbonate has been widely used as materials for housings or parts of various computers (e.g., a desktop computer and a notebook computer), printers, word processors, copying machines and the like.
In recent years, with respect to a shaped article obtained from an aromatic polycarbonate, especially in the case where it is intended to use the shaped article as a housing, it has been strongly desired to reduce the thickness of the shaped article so as to reduce the weight thereof. However, a thin housing is likely to suffer distortion by external stress or under the load of the parts inside the housing. Therefore, there has been a strong demand for aromatic polycarbonates having high stiffness and high dimensional precision.
In an attempt to improve the stiffness and dimensional precision of an aromatic polycarbonate, a method has been proposed in which an inorganic compound, such as a glass fiber, a carbon fiber, talc, mica or wollastonite, is blended with an aromatic polycarbonate as a reinforcing agent and/or a filler.
However, an aromatic polycarbonate resin composition containing an inorganic compound poses a problem that, during the molding of the resin composition, the inorganic compound promotes the decomposition of the aromatic polycarbonate. Especially the use of a basic inorganic compound, such as talc or mica, in an aromatic polycarbonate resin composition poses a problem that the melt stability of the resin composition is markedly lowered, so that the properties of the resin composition are markedly impaired during the molding thereof.
For solving the above-mentioned problems, various proposals have been made for suppressing the lowering of the molecular weight of an aromatic polycarbonate (i.e., for suppressing the decomposition of an aromatic polycarbonate). For example, Unexamined Japanese Patent Application Laid-Open Specification No. Hei 2-283760 proposes the addition of a phosphorus compound; Unexamined Japanese Patent Application Laid-Open Specification No. Hei 3-21664 proposes the addition of an organic acid; and Unexamined Japanese Patent Application Laid-Open Specification No. Hei 10-60248 proposes the addition of a sulfonic acid phosphonium salt. However, even by these proposals, the melt stability of the resin composition, especially at high temperatures, was still unsatisfactory, so that the molding temperature of the resin composition is inevitably limited, that is, only a relatively low molding temperature can be employed.
On the other hand, with respect to aromatic polycarbonate resin compositions used for office automation machines, and electric and electronic appliances, it has been desired to achieve excellent flame retardancy as well as excellent stiffness and dimensional precision. Further, in recent years, from the viewpoint of environmental protection, it has been desired to develop a flame retardant aromatic polycarbonate resin composition which contains neither a bromine compound nor a phosphorus compound as a flame retardant.
For example, Unexamined Japanese Patent Application Laid-Open Specification No. 2002-80709 describes an aromatic polycarbonate resin composition which is obtained by blending an aromatic polycarbonate with an inorganic filler, an organophosphorus flame retardant and an alkali metal salt of an organic acid. This patent document describes that the flame retardancy of the obtained resin composition is “V-0” as measured in accordance with UL-94 standard with respect to a test specimen having a thickness of 0.8 mm. However, the resin composition described in this patent document is disadvantageous in that a phosphorus compound is used as a flame retardant, and that the properties of the resin composition are markedly lowered under high humidity and high temperature conditions.
Further, Unexamined Japanese Patent Application Laid-Open Specification No. 2002-294063 describes a resin composition which is obtained by blending an aromatic polycarbonate with a metal salt of an organic acid, an alkoxysilane compound, a fluorine-containing polymer, an inorganic filler, and optionally an organosiloxane compound. This patent document describes that, when the above-mentioned organosiloxane compound (optional component) is used, the flame retardancy of the obtained resin composition is “V-0” as measured in accordance with UL-94 standard with respect to a test specimen having a thickness of 0.8 mm. However, since the resin composition described in this patent document contains an organosiloxane compound which has a low heat stability, disadvantages are caused in that, when the resin composition is molten at high temperatures, the resin composition is likely to suffer discoloration and the amount of components volatilized from the molten resin composition increases.
Furthermore, Unexamined Japanese Patent Application Laid-Open Specification Nos. 2003-82218 and 2003-268226 describe a resin composition which is obtained by blending an aromatic polycarbonate with a fluorine-containing resin and a silicate compound. However, the resin composition described in each of these patent documents is unsatisfactory with respect to flame retardancy and melt stability.
As apparent from the above, in the prior art, it has been impossible to obtain an aromatic polycarbonate resin composition, which contains an inorganic compound, and which not only exhibits a high flame retardancy in the form of a very thin shaped article thereof without using a bromine compound or a phosphorus compound as a flame retardant (for example, “V-0” as measured in accordance with UL-94 standard with respect to a test specimen having a thickness of 1.2 mm, or “5VB” as measured in accordance with according to the UL-94 standard with respect to a test specimen having a thickness of 1.0 mm), but also has excellent melt stability and mechanical strength. Therefore, it has been desired to develop such an excellent aromatic polycarbonate resin composition.